Television transmission



Oct. 9, 1934. J. v L. HOGAN 1,976,699 I TELEVISION TRANSMISSION Filed Aug. 3, 1929 5 Sheets-Sheet 1 l NVENTOR 9, 1934- J. v. 1., HOGAN 1,976,699

TELEVISION TRANSMISSION Filed Aug. 5, 1929 3 Sheets-Sheet 2 NVENTOR Oct. 9, 1934. J v H G 1,976,699

TELEVISION TRANSMISSION Filed Aug. 3, 1929 3 Sheets-Sheet 3 QTHIS l5 EAVSAMEPLE 0d 2"" 5AM r: mm d A .1. u

AMPLIFIER $25 a MlTTE MOTOR L Y J Patented Oct. 9, 1934 1,976,699 7 I retcvrsron TRANSMISSION John V. L. Hogan, Forest Hills, N. Y., assignor to Radio Inventions, Inc.,- New York, corporation of New York- N. Y., a

Application August 3, 1929, Serial No. 383,200

2 Claims. (CL 178-6) The primary object of, this invention is to make possible the transmission and reception of printed or-written matter, and the like, by electrical methods including so-called television. objects will appear from the following description.

-In certain methods of electric picture transmission, the'view to be transferred from sendingv 1 5 mitting arrangements, e. g., those in which a plurality of channels are used for the concurrent transmission of two or more elementary areas.

Atypical picture transmission involves the successive delivery, over a wire or radio communication channel, of impulses whose, instantaneous value is proportional to the intensity of illumination, or brightness of each given elementary area, beginning, for example, at the upper left and ending at the lower right of the view. If

only a single picture is to be transmitted, one such series of impulses ordinarily suffices. If motion'pictures or the effect of continuous vision is to be produced, the scanning process is repeateda fraction of a second later and, indeed, is substantially continuous, the successive views being scanned and transmitted sufiiciently 'frequently to permit their recombination at the receiving point with the aid of the'phenomenon, i

' having only 30 elements in the horizontal direction it is obvious that only three elements would 90 of visual persistence in the eye or in the receiving apparatus or both.

The invention may best be understood by reference to the hereinafter specification and the drawings which constitute a part thereof, to wit:

Fig. 1 represents the field of view as composed 40 of anumber of elemental areas.

Fig.2 shows a human figure drawn in 21 elemental areas. V

Fig. 3 shows the typical reproduction of a figure such as shown in Fig. 2 as received in a picture-transmission system.

' Fig. 4 shows a human figure drawn in 192 elemental area's.

Fig. 5 shows the reception of a picture such as Other pattern such as Fig. 3 side by side.;

Fig. .8 shows in plan and elevation an analogous method of transmitting; a title or caption, according to my invention.

Fig. 9shows a border used as a position datum.

Fig. 10 shows in diagrammatic for m a simple but typical radio television transmitting and receiving system. r 5 7 Referring to Fig. 1, there is shown the normal field of such a transmission, divided into 720. elementary areas, as is the case when the view-6d is scanned along 24 lines extending horizontally anddisplaced vertically and has a length to height ratio of 10/8. This is a common division television. Itis obvious thatno element of a view smaller than one of the elementary areas shown can give a full black or full white impression in transmission, even though initself it may be dead black or clear white. Consequently the detail of'any view that can be transmitted is substantially limited by the number of elementary 76- areas, and in general details can be recognized at the receiving point only when they are of sumcient size to include substantiallythewhole of one or moresuch areas. 1

In many instances it is desirable to utilize sub- 80 stantially; the entire vertical field in order to transmit the maximum amount of detail. For example, if portraits of a group of ten persons are .to be transmitted it is obviously desirable that each portrait shall be shown with the greatest possible. 85,

, definition in order that its identifying and individual characteristics shall be seen. If pictures of ten individuals were to be projected on a screen be available for each of the ten individuals stand ing or sitting side by side. On the basis of normal proportions, from seven to ten vertical elements a would be required for each human figure. Figure 2 shows at A such a figure drawn within 95,. the available area of 3 x 7 elemental areas from Fig. l, Since detail corresponding to nothingsmaller than a single elemental area can be transmitted, it isquite clear that the 27.;areas availableto each figure will not show enough 9 detail to make it recognizable -in fact-such a ,figure will be reproduced substantially as indi cated in Fig. 3, and the group of ten standing per-, sons would show as ten lateral repetitions of a Even if thefull twenty-four vertical elements are utilized forja single figure, only about eight will be used in the horizontal direction. Threev figures can thus-be distributed across the total field, but the detail of each will be extremely vague 110,

, 12 *vertical" elements. lit i's' cle'ar that with-less trim-1'2 vertical e e entsith'e iidentityof'-'various near element's from-e to T2 horizontal el ments are required per letten'a-nd consequently not more than twoto four letters can-be shownsimultane lesser degreei With 48 x field'it becomes poissie ble' to show; from 4 to S -letters simultaneouslyor hown'mways a summg that the' 'detail of these that the j-whole view is' 't'ransinitted' iv-ithout any- I aftitle eompiism e e than twoor'fthreefsliort Words; f-In" the" absence of fany methodo Feverout one -l'et'te'r or one short wordat a time:- I

proved unsatisfactory. 60"" L '7 tion ,'-along t'itle-or sentence fortelevision transmissionmaybef'prepared 'by printing it-iipon a "paper strip whi-ch -is passed before a n'lotior'r-pic v text as though the observers eye were passing along the printed line, and by reason of the large and clear lettering used and the continuity of motion the text is easily read without much regard to its total length.

It is possible to dispense with the intermediate step of making a motion picture film of each view or'printed strip to be transmitted iffthe television is used for a head it becomes possible to show transmitted is of such character that the objects enough detail of the features to permit some "d'eor letters to be transmitted can be caused to pass gree of personal identification. The two head's-Iac'ross its field of view by suitable relative motion. Turning to the television receiving apparashown on 24 vertical elements in Fig 6. are obv viously recognizable as pictures of two difl'ere'nt' tus, it shouldbe noted that any lack of exact persons. .synchronism between sender and receiver will The same difiiculty of -transmitting adequate causethe imagejat the receiver to appear to float detail to permit recognition appears when one. out of. the field of View, usually either to the right attempts to transfer printed or written copy in a or left. In operating such receiving apparatus it field of relatively small tetaifiamber'tf elemental "'iscu fl ma y t0 djus the Speed Of the receiving areas. For the sake of illustration we may-cone .s annin vi so h th im s remain c nsider the minimum number of elements that will tered in the field of view of the receiver. Conpermit' easy recognitioiiofthe simplest blocksequently a'rece'iving operator who interceptssuch form of'capitalletters-fi Fig. 7 shows the lettersA,B, an'd CxQ"withand evidently insufficient to transmit recognizable portraits. As indicated in Fig. 4 and Fig. 5, drawn on 8 x 24 elemental areas and having the same relation as Figs. 2 and 3, a1l three human figures will look substantially alike and only the most striking differences will permit differentiation. '1 :fl i: .f

On theother hand, n? the .full' field vertically.

letters-is quite-uncertair'ijand that-the- .e ofeven more than 12 is desirable. With'-twelve;ver-"' tween" sender and receiver and produce: unsatisposition by either the manual or-automatic synto transmit aging-1e shortword, With 60 572 bars at each side of the view, one or more-dots or field, a were of" 6 {w lO-letters cente 's-momma.- I With -12 0"x "1'44ashort'group ofwdrds can be venient -check on the speed adjustment of. the

receiving scannerw relativelyfinely dividedfields is'accurately transo p t i mitted softha't each elemental area is given "its properfghc-i nlfie'nsity value. 'As 1 well'f known; such-fidelity of transmission isexce'e ng difii cult of attainment. 5* Frornthe' above is "evidentathat, with the present limitations of television it-i's -'ext 1 "emely unseen if not impossible to traiismit affre6og f ni'zable pict'u -'0f more t'han two{ individuals for rangedas-usual) in the rotating scanning disc K each scanning hole falls .uponthe photoelectric coming gthis di'flicu'l't'yf it has 1 been 'propo'sedfthav the portraits of group or individuals be tra'ns mitted individually-"andsuccessively} orF that the titlebe transmitted by spelling them} lated currents impressed on the antenna-ground su'cli'method's of transmission-'lack the element y t 1 in a i n orfedntmuity {and- Show no rela tionshi a yin th 'p r dula n the successively transmitte According 'to my inventionyI transmit as much of the total view-as can be clearly see the field-of the apparatus'an'd then-movethe field of v-iew progressively/tandpreferably uniformly so other variable intensity lightsour'ce at Q'. A synbread;- thatfwould' la'tionjship of its parts:

ar its" ontinuity and the re-' -15. :1: orifices fromzD is seenby theeye of'the observer "Accordingt one-wa s: p clti'c'lng myinvenmitter is thus reconstructed .atthe receiver."

It will be understood that the System 1 have. describedforthe purpose of overcoming certain tur'e" {copy-mg camera "at "such distance} that-the letters occupy' preferably' at least to of "the vertical dimensionof'thefie'ld, as shown in Fig. 8; whetherfiused to reproduce silhouette-or half tone vision'systmg thereceiver will reproduce the Many variations of the general system-maybe radio system adapted for use of panoramic: film such as -described-is illustrated in Fig- 10. 'The prepared film'passes' with the customary intermittent motion from reel A to re'el Bs For the fraction'of'a second-required to scan onetframe' of the film it. remains stationary-between'the lenses DandE, light' from the lamp-C passing through the orifices (spirally ar currents selected, amplified'and rectified by' the" difiiculties imposed by'thelim-itation of detail-that" can be transmitted by televisio'n-is applicable drawings, photographs, views'or letters.

factory results. "I therefore prefer toprovide-in" P each such-view a fixed datum point ormark which Will indicate 'a' position past whichthe' objects' or letters are moved, and Which-mayL- be held in ohronism control of the receiving apparatus. 1 Such datum may take the form, 'for example; of a frame or border: (Fig. 9), apair of vertical:

figures, etc.' This datum or 'indexprovides a con-' udrivenbymotor M. Phelightpassin'g through cell F, --.giving E-IlSB to electrical impulses which are-amplified at G and causedto modulate the continuous radio a frequency current generated by the radiotransmitter H. These picture-modu At thereceiver' the waves areintercepted by at P and are then impressed upon a glowlamp or chror'iousyscanning disc R of the usual type is driven by motor C and light passing'throughsits" at T. "The picture originally scannedat thet-ransi 1,976,699 3' utilized, e. g., titles or sketches may be shown in the act of being lettered-or drawn upon the field of view (preferably toward one side thereof) and streaming off out of sight as they are completed. Moreover, although I have described the invention in relation to a system involving essentially square picture elements, the improvement is useful with circular, rectangularor other forms of elementary area. 1 I The present invention is to be distinguished from so-called talking signs which are specifically for the purpose of exhibiting long sentences or groups of words by electric lights automatically switched to produce an illusion of motion. No space limitations are involved, nor is there any limitation as to the amount of detail that can be shown (1. e., the number of lamps allotted to each letter). Similarly, the present invention is to be distinguished from motion-picture projection upon the screen of panoramic landscapes and the like. In motion-picture projection there is no lack of detail and the only purpose of moving the camera is to include more of the view than could be seen by the human eye (or recorded by the "camera lens) in a single position. In contrast to both of these, television transmission is so limited in picture detail that in many instances the images received cannot be recognized unless by some method the observer is told what to look 'for. Even under the best transmission conditions I have found that a vastly better appreciation of the transmitted pictures can be given to the observer if explanatory notes and titles are freely interspersed with the pictures.

These notes may be prepared and transmitted as explained above in connection with Figs. 8 and 9, just as are the pictures of other subjects, and the same rules apply as to the necessity of including sufficient vertical and horizontal elemenftary areas to provide adequate detail.

Variations in the design and condition of adjustment of the apparatus and of the condition of the transmitting medium often result in distortion which tends to destroy the identity of the image. It is therefore desirable to use as many vertical elements as possible so as to produce a maximum clarity in the reproduction.

It should be borne in mind that the amount of detail in the transmitted picture is a function of the number of elements into which it is divided rather than the magnification of the image. Present practice would suggest a. minimum limit of say 24 by 30 and a maximum of about 160 by 200 and an intermedate range of about 48 by 'as desirable under various conditions.

For simplicity in illustration I have omitted half tone efiects and limited the drawings of transmitted images to black and white. The principle exemplified, however, is applicable to all gradations within the scope of the instrumentalities available.

By this system it will be understood that it is desired to transmit from one point to another an image of a subject. This is done by sending successive views of parts of the subject, which views are reconstructed into the desired final image or duplicate representation of the subject.

The image of course is what the observer sees. By this method I reproduce in effect panoramic or other pictures with what may be termed run-v ning titles which titles may be of indefinite length and consist of letters of sufficient size to be readily distinguished so that unlimited explanatory facility is provided.

Because of the fact that the television system described utilizesthe-phenomenon of optical persistance to give the illusion of continuous vision in spite of the transmission of separate views taken -at short intervals of time, the displacement of the subject in the field of view must not be too greatbetwee'nany one view and the next. Otherwise the result'will-be confusing tothe observer, producing the appearance of too rapid motion-or even of overlapping images." In transmitting a line'of text at therate of-loviews per second, I have obtained excellent results by adjusting the speed of lateral motion from left to right so that any given letter appeared to cross the full field of view from right to left (i. e., the field of view appeared to cross that letter in the direction of normal reading, from left to right) in from 1.5 to 3.5 seconds. This does not represent the useful limits of such motion, since either faster orslower translation may be utilized so long as on the one hand the impression does not become confused nor, on the other, the time available for transmitting the entire subject is not exceeded. In the above instance the vertical dimension of each letter was about of the total height of the field of view, and from four to six letters or equivalent characters or spaces appeared across the field at the same time.

By increasing the number of views per second the time rate of motion may be increased without confusion. When smaller letters are used, so that more appear in the field at the same time, the time rate of motion should be decreased. In television it is customary to transmit from 7 to 20 views per second, or thereabout, and with characters occupying a substantial fraction of the 110' vertical dimension of the field of view it is desirable to adjust the motion so that the displacement between one view and thenext is not much greater than 1/20th of the dimension in the direction of motion, so that the same character or 115 object (or some part of it) will remain visible during the time of at least 20 views. I have had good results with the motion adjusted so that part or all of a single object remained in sight during the time of about 60 successive views.

In the claims the use of the terms subject and object is intended to apply broadly to all animate and/or inanimate bodies and/or to one or more letters or words as they may appear in the views to be transmitted.

I claim:

1. In a system of electrical transmission of images of a writing, the combination of means at the transmitter for analyzing the subject into successive views each consisting of elemental areas, a carrying film having successive views of parts of said writing, said views being disposed at substantially equal intervals along said film and each letter of said writing occupying more than one-third of one dimension of said view, successive views being progressively displaced laterally at substantially uniform increments of distance from a margin of the film,

means controlled by the film for producing elec- I carried by said film, means for conveying said impulses to a receiver and means at the receiver for synthesizing and observing whereby the ob-. served image appears to move at a substantially uniform velocity across the line of vision so that said writing shall be reproduced in the proper temporal and spacial sequence. v I

2. In a system of electrical transmission of images of text characters, the combination of 150,1

means atthe transmitter for analyzing the subject into elemental areas, a record carrying said 7 textcharacters and adapted to be moved in-the direction of the normal succession of said characters, each. characteroccupying more than onethird of the narrower dimension-:of thefield of scanning, means for moving said record continuously in one directionso asto display said characters intheir normalsequence, means con-j trolled by said record forv producing electrical- 

